The 31-year-old striker admits he struggled for motivation in some games before inheriting the armband.
"I think [I have changed], yeah," he told Arsenal's matchday programme. "Because you feel a lot of responsibilities and I think I am trying to give everything in every single game.
"I think before maybe, I don't know, it was not done on purpose but maybe sometimes I was a little bit less concerned on certain games.
"But now I am just focusing on every game and trying to give my best. Even if I'm on the bench I try to scream and help my team-mates, so yeah I think it's changed me.
"I think this is really important because sometimes you can also have bad days and be in a bad mood, so you have to try to change it into positive things.
"This is where I am, how can I say, it's easy for me to make people maybe happier: to lift them up and that's my job. I can say that's my job but I do it naturally.
"I just have to be the example for everyone. If I have to go to the gym to do the upper body I have to go first, then everyone will follow.
"Because the guys in the gym are waiting and say, 'If you come then everyone will come! You know that!' So I say 'OK, OK' so now I am the first to go to the gym, this is it."